Heart valves permit unidirectional flow of blood through the cardiac chambers to permit the heart to function as a pump. Valvular stenosis is one form of valvular heart disease that prevents blood from flowing through a heart valve, ultimately causing clinically significant heart failure in humans. Another form of valvular disease results from heart valves becoming incompetent. Failure of adequate heart valve closure permits blood to leak through the valve in the opposite direction to normal flow. Such reversal of flow through incompetent heart valves can cause heart failure in humans.
The human mitral valve is a complicated structure affected by a number of pathological processes that ultimately result in valvular incompetence and heart failure in humans. Components of the mitral valve include the left ventricle, left atrium, anterior and posterior papillary muscles, mitral annulus, anterior mitral leaflet, posterior mitral leaflet and numerous chordae tendonae. The anterior leaflet occupies roughly ⅔ of the mitral valve area whereas the smaller posterior leaflet occupies ⅓ of the area. The anterior mitral leaflet, however, hangs from the anterior ⅓ of the perimeter of the mitral annulus whereas the posterior mitral leaflet occupies ⅔ of the annulus circumference. Furthermore, the posterior mitral leaflet is often anatomically composed of three separate segments. In diastole, the anterior leaflet and the three posterior leaflets are pushed into the left ventricle opening. In systole, the leaflets are pushed toward the plane of the mitral annulus where the posterior leaflets and larger anterior leaflet come into coaptation to prevent blood flow from the left ventricle to the left atrium. The leaflets are held in this closed position by the chordae tendonae. Dysfunction or failure of one or more of these mitral components may cause significant mitral valvular regurgitation and clinical disease in humans.
Surgical treatment has been the gold standard since its introduction in the 1950s. Currently, there are two surgical options offered for treatment. The first, mitral valve replacement, requires complex surgery using cardiopulmonary bypass to replace the mitral valve using a mechanical or bioprosthetic valvular prosthesis. Although a time-tested and proven strategy for treatment, bioprostheic valves suffer from poor long-term durability and mechanical valves require anticoagulation. As an alternative, surgical mitral valve repair has emerged as a superior procedure to achieve mitral valve competence and normal function. This operation is really a collection of surgical techniques and prostheses that collectively are referred to a mitral valve repair. Each component of the mitral valve can be altered, replaced, repositioned, resected or reinforced to achieve mitral valve competence.
Mitral annuloplasty has become a standard component of surgical mitral valve repair. In performing this procedure, the circumference of the mitral valve annulus is reduced and/or reshaped by sewing or fixing a prosthetic ring or partial ring to the native mitral valve annulus. As a consequence of mitral annuloplasty, the posterior mitral leaflet often becomes fixed in a closed position, pinned against the posterior left ventricular endocardium. The opening and closure of the mitral valve is subsequently based almost entirely on the opening and closing of the anterior mitral valve leaflet.